Dunbar struggled to stay healthy during his lone season with the Seahawks in 2020, appearing in just six games while producing the worst campaign of his career, according to PFF.
He spent time on the commissioner's exempt list during the 2020 offseason after being arrested following an alleged armed robbery in Florida. The charges against him were eventually dropped.
The 28-year-old played for the Washington Football Team for his first five seasons after joining the club as an undrafted rookie out of Florida in 2015. He averaged 42 tackles, two interceptions, and 10 pass breakups per 16 games played with Washington.
He was traded to the Seahawks for a fifth-round pick after the 2019 season.
The cornerback position has recently been an area of concern for the Lions, who lost veterans Justin Coleman and Desmond Trufant in free agency this offseason. Detroit attempted to address the unit with its selection of Jeff Okudah at third overall last year, but the former Ohio State star disappointed as a rookie.
Opposing quarterbacks posted a league-high 112.4 passer rating against Detroit in 2020.